The invention relates to a device for conveying sheet-type, flat items that preferably consist of a flexible material, in particular sheets of paper, the device comprising a feed-in region provided with a lower feed conveyor for conveying and successively feeding in the flat items, a discharge region that follows the feed-in region in a downstream direction and is provided with a lower discharge conveyor for discharging the flat items, a joint upper belt conveyor that extends across the feed-in region as well as the discharge region and has a lower belt section, arranged above the lower feed conveyor, to allow the top of a flat item positioned on the lower feed conveyor to make contact with the joint upper belt conveyor, as well as an overlap device for generating an overlapping flow of flat items in the discharge region.
German Patent document DE 27 25 547 A1 discloses a device installed downstream of a cross-cutter, which is used to form an overlapping flow of flat items such as sheets or magazines. This known device comprises fast-moving upper belts, jointly guided across a feed-in region as well as a discharge region, fast-moving lower belts in the feed-in region and downstream arranged slow-moving lower belts in the discharge region, wherein the slow-moving lower belts in the discharge region act as deceleration belts and generate the overlapping flow. The fast-moving upper belts with their lower belt sections in the discharge region can be adjusted slightly in height by eccentrically positioned rollers to correspondingly adjust the distance to the slow-moving lower belts, so as to adapt to the thickness of the overlapping flow to be generated. This known device is furthermore provided with an overlap finger and a downstream arranged suction box, which can be adjusted either in the conveying direction or counter to the conveying direction. A braking roll is arranged on the upper side, downstream of the suction box, and is provided with an associated support roller that is positioned on the lower side.
German patent document DE 14 61 244 A1 discloses a device, installed downstream of a cross cutter, for slowing down paper sheets or the like in order to generate an overlapping flow. This known device comprises fast-moving upper belts that are followed downstream by slow-moving upper belts, and fast-moving lower belts that are followed downstream by slow-moving lower belts, which function as deceleration belts. Furthermore provided is an overlap finger with a braking roll or a deceleration belt. A free-wheeling contact roller is arranged downstream of the overlap finger.
German patent document DE 29 39 377 A1 discloses a device, following downstream of a cross cutter, for slowing down and overlapping paper sheets. This device is provided with fast-moving upper belts that extend across a feed-in region as well as a discharge region, and fast-moving lower belts in the feed-in region that are followed in the discharge region by downstream arranged slow-moving lower belts, functioning as braking belts. Furthermore provided are an overlap finger and a following braking roll. The braking roll has a flattened section to prevent pressure from being applied to the leading edges of the paper sheets, which are already arranged overlapped and thus scaled at this location.
German patent document DE 31 18 746 A1 describes a device installed downstream of a cross cutter for picking up and conveying sheets having an undesirable pre-bending. This known device is provided with upper and lower belts, which can be adjusted in the conveying direction and counter to the conveying direction. In addition, the intake angle between upper and lower belts can also be adjusted.
German patent document DE 39 40 960 A1 discloses a device installed downstream of a cross cutter for slowing down sheets to be deposited in a stack, in particular sheets of paper or cardboard. This known device is provided with a group of accelerating upper belts and lower belts, as well as a downstream installed pair of braking rolls. The braking rolls have a profile that allows for a continuous deceleration of the sheets. This known device is designed to generate an overlapping flow shortly before the stack front is reached, wherein this overlapping flow is generated according to a first example with the aid of a suction box and according to a second example directly with the aid of the pair of braking rolls.
German patent document DE 199 45 114 A1 and the associated European patent document EP 1 214 264 A1 describe respectively a device, installed downstream of a cross cutter, for generating an overlapping flow. This known device is provided with a transfer-out device, accelerating upper and lower belts, as well as a suction box with a downstream-positioned lower belt that functions as a braking belt. The distance between the upper belts and the conveying plane can be adjusted to adapt to the thickness of the overlapping flow to be generated. The upper and lower belts can furthermore be adjusted in a conveying direction and counter to the conveying direction for the purpose of a format adjustment. The transfer-out device is furthermore embodied so as to pivot for removing a jam.
German patent document DE 20 2004 005 827 A1 and the corresponding PCT publication WO 05/097647 A1 respectively disclose a device that is installed downstream of a cross cutter and is designed to generate an overlapping flow. This known device comprises a transfer-out device, accelerating upper and lower belts, as well as a suction box with downstream arranged braking belts. Pivoting braking rolls are arranged above the braking belts, such that they can act by an adjustable spring force onto the sheets, which are already overlapped at this location.
When generating an overlapping flow with the aid of the above-described devices, the processing speed inside the machine can be increased considerably, not least because the impact energy is noticeably lower when entering the stacking region.
However, generating an overlapping flow is not advisable for papers with extremely sensitive surfaces because of the high danger of damage caused by the overlapping. In particular items belonging to the product spectrum of paper sheets with a shiny surface, such as photographic paper, cannot tolerate overlapping because the cut edge as well as the backside of the overlapping section of the paper sheet can leave interfering marks or flaws on the shiny surface.